lua-resty-snappy

lua-resty-snappy provides LuaJIT FFI bindings to Snappy, a fast compressor/decompressor (https://code.google.com/p/snappy/).

Installation

Just place snappy.lua somewhere in your package.path, preferably under resty directory. If you are using OpenResty, the default location would be /usr/local/openresty/lualib/resty.

Compiling and Installing Snappy C-library

1. Install snappy with your operating system's package management OR build it manually from the sources provided from Snappy repository.
2. Check that you have snappy.so (or .dylib, or .dll) somewhere in the default search path for dynamic libraries of your operating system (or modify snappy.lua and point ffi_load("snappy") with full path to snappy.so, e.g. local json = ffi_load("/usr/local/lib/lua/5.1/snappy.so")).

Using LuaRocks or MoonRocks

This will only install the Lua module, not the Snappy C-library.

If you are using LuaRocks >= 2.2:

$ luarocks install lua-resty-snappy

If you are using LuaRocks < 2.2:

$ luarocks install --server=http://rocks.moonscript.org moonrocks
$ moonrocks install lua-resty-snappy

MoonRocks repository for lua-resty-snappy is located here: https://rocks.moonscript.org/modules/bungle/lua-resty-snappy.

Lua API

Error Codes

  SNAPPY_OK               = 0
  SNAPPY_INVALID_INPUT    = 1
  SNAPPY_BUFFER_TOO_SMALL = 2

string, len snappy.compress(input)

Compresses input with Snappy algorithm, and returns compressed data and its length. On error this will return nil and an error code.

Example

local snappy    = require "resty.snappy"
local comp, err = snappy.compress("test")
if comp then
    -- do something with compressed data and length
    -- (length is stored in err value)...
else
    if err = 1 then
        print "Invalid input"
    elseif err == 2 then
        print "Buffer too small"
    end
end

string, len snappy.uncompress(compressed)

Uncompresses compressed with Snappy algorithm, and returns uncompressed data and its length. On error this will return nil and an error code.

Example

local snappy      = require "resty.snappy"
local uncomp, err = snappy.uncompress(snappy.compress("test"))

number snappy.max_compressed_length(source_length)

Returns maximum-possible length as a number of bytes of compressed data when uncompressed source_length is given. This is used to create buffer for compressing, but can also be used in quick measurement (and it may have nothing to do with final compressed output length, other than it cannot be larger than what this function returns).

Example

local snappy = require "resty.snappy"
local number = snappy.max_compressed_length(1000)

number snappy.uncompressed_length(compressed)

This is quicker way (than using snappy.uncompress to determine how many bytes the compressed data will be when it is uncompressed.

Example

local snappy = require "resty.snappy"
local number = snappy.uncompressed_length(snappy.compress("test"))

boolean snappy.validate_compressed_buffer(compressed)

This can be used to check if the compressed bytes are actually Snappy compressed bytes or something else. I.e. something that can be uncompressed with Snappy.

Example

local snappy = require "resty.snappy"
local bool   = snappy.validate_compressed_buffer(snappy.compress("test"))

License

lua-resty-snappy uses two clause BSD license.

Copyright (c) 2014, Aapo Talvensaari
All rights reserved.

Redistribution and use in source and binary forms, with or without modification,
are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice, this
  list of conditions and the following disclaimer in the documentation and/or
  other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR
ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.